Genetic data reveal wintering ground affiliation of humpback whales from the Mexican Central Pacific

Abstract

Two groups of humpback whales inhabit the waters off the Pacific coast of Mexico the coastal wintering aggregation in the north (MX), and the southern Mexico/Central America wintering aggregation (S‐MX/CEA) in the south. However, along the coast of the Mexican Central Pacific (MCP), the population affiliation of humpback whales is uncertain. Some studies have concluded that the MCP whales are part of S‐MX/CEA, while others have suggested that the MCP may represent an overlap zone between the two wintering aggregations. In this study, data from 354 biopsy samples were collected over a 12‐year period, to provide insight from genetic information into the affiliation of MCP whales to and the boundaries between the wintering aggregations. Using mitochondrial control region sequences, we found that the majority (73%) of MCP whales are part of MX, but that the boundary between the two wintering aggregations may shift latitudinally depending on environmental conditions. The high haplotypic (h ± SD = 0.859 ± 0.0138) and nucleotide diversity (π ± SD = 0.0145 ± 0.0075) of the MCP whales are also consistent with our sample, including animals from both wintering aggregations. More research is needed to better describe the ranges of the MX and S‐MX/CEA wintering aggregations to ensure their successful conservation and management.

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“…These subset models could not be considered absolute abundance estimations because each 3-year sample was not assumed to be a closed population or controlled for sample bias such as, in the case of Mainland Mexico, an overlap of Central American whales. These whales are known to co-occur using the region as a migratory corridor [ 46 , 76 ], and therefore the subset abundance estimate sampled a population with undefined boundaries. In Hawai‘i, sample effort was concentrated in the Maui-Nui channel and to lesser extents off the islands of Hawai‘i, Oahu and Kauai, without a clear definition of whether this is a comprehensive sample of an equally mixed Hawaiian island population.…”